Loading movieclip in library

Ok I feel stupid because I can load an external movie but I can’t load a movieclip from within the library…can anyone help me out please…

 stop(); 
_root.onEnterFrame = function(){
 _root.load_nav.loadMovie("box_buttons");
}

That’s the code I used, but for reason I can’t get it to work… :frowning:

Thank you,

Boon